At 13 years old, it's probably getting towards the end of its useful life. You seem to have tried most things? Have you taken the cover off the unit and cleaned all of the dust out of it? I'm sure after 13 years, that some dust has gotten into the internal components? If you have the ability, I'd also have a quick look at some of the solder joints, to see if they haven't dried out. If you are competent with a multi-meter, you could see of the internal remote control wiring connections in the AVR are working correctly. Apart from that, as I said, it just may be past its use-by-date, nothing lasts forever. I'm sure others will be able to give you some advice as well. Good luck.